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bio website vyznev.net
location Helsinki, Finland
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visits member for 2 years, 8 months
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I'm not really a cryptographer, I just play one on the internet.

Seriously, I'm just a programmer and mathematician interested in puzzles and information security. I don't have any kind of formal crypto training, but I've picked up a few things here and there over the years. Topics I'm particularly interested in include protocol design and analysis, classical ciphers and information-theoretically secure crypto techniques such as one time pads and secret sharing schemes.

Please consider any (original) code I post to Stack Overflow (and other Stack Exchange sites) to be released under CC-Zero unless stated otherwise. You may do whatever you want with it and don't have to credit me in any way, although of course that would be nice.


Apr
29
comment Secure order preserving hash function
@curious: If I can choose a string and ask you for its hash, then the attacks still works. Even if I can only ask whether the hash of my string is less than the hash of your string, that's still enough information for this attack.
Apr
29
revised Secure order preserving hash function
edited tags
Apr
29
answered Secure order preserving hash function
Apr
29
answered what is the difference between Scrypt and PBKDF2
Apr
29
comment Counter Mode: static IV but different keys
...or maybe Does AES-CTR require an IV for any purpose other than distinguishing identical inputs?
Apr
27
awarded  Necromancer
Apr
27
comment Attacking historical ciphers methodology
The Hill cipher isn't exactly unbreakable either. (Mind you, that question concerns a known-plaintext attack, but you could always do crib-dragging. Actually, it might be possible to use frequency analysis and linear algebra for a direct ciphertext-only attack... need to think about that a bit more.)
Apr
27
answered implementing long term archive encryption
Mar
30
comment Using encryption schemes for identification
I think you need to define your attack scenario a bit more precisely. In particular, can the attacker impersonate B to A? If so, they can carry out a straightforward MITM attack by just using the real B as an oracle. If not, why do you even need an authentication protocol?
Mar
22
comment What is the difference between a hash and a permutation?
@Nik: While there are various definitions of what constitutes a hash function, I don't think your example would qualify under most of them. Certainly it's not a hash function in the sense we usually use in cryptography. Still, you do have a point: if we restrict our hash to a set of inputs equal to its set of possible outputs, the thus restricted function could be a permutation. Most cryptographic hashes still won't be, though.
Mar
22
answered What is the difference between a hash and a permutation?
Mar
5
comment is AES secure for java application licensing
Digital signatures are a form of public key cryptography (but they don't generally involve encryption, although some algorithms such as RSA can be used for both). Their advantage in your situation is that the software only needs to contain the public half of the keypair, which can be used to verify signatures but not to create new ones. Of course, distributing a modified copy is still possible, but considerably less convenient for the cracker than simply distributing keys to unmodified copies.
Mar
5
answered is AES secure for java application licensing
Mar
2
comment Why is CAMELLIA suddenly so widely used?
@CodesInChaos: Indeed, this seems like a silly reason, given the existence of SSLHonorCipherOrder and similar options for other servers. Still, +1 to Jumbogram for figuring out the reason, even if it's silly.
Mar
1
revised How to solve the reverse of an equation that uses MOD?
copyedit
Mar
1
reviewed Approve suggested edit on How is CipherCloud doing homomorphic encryption?
Feb
27
comment Why do we need to hash both the message and the $h$ value in ElGamal signature?
I tried to clean up your question a bit, but there were some places where I wasn't really sure what you meant. Could you please check that I didn't introduce any mistakes, and maybe try to clarify your question further.
Feb
27
revised Why do we need to hash both the message and the $h$ value in ElGamal signature?
added 52 characters in body; edited tags; edited title
Feb
27
wiki created elgamal-signature description
Feb
27
wiki created elgamal-signature excerpt